1. Field of the Invention
The present invention relates to microwave cooking of foods, and more particularly to a patterned microwave susceptor element and container incorporating same.
2. Description of the Related Art
The principle behind the cooking of foods in a microwave is well known. Briefly, food product is excited by the microwave energy and molecules of the food product become excited to produce heat. Characteristically, the food product cooks more quickly on the inside than on the outside, compared with conventional oven cooking. If browning or crisping of the exterior of the food product is desired, the food product is placed in a container that includes an element known as a susceptor. The susceptor packaging typically is made of microwave interactive material and absorbs, reflects and transmits microwave energy in varying proportions depending on the type of food product and its working condition in the microwave oven. The surface to be browned is placed near the susceptor. The susceptor becomes hot through microwave absorption when exposed to microwave energy, thereby increasing the amount of heat supplied to the food product exterior to promote surface browning. Some of the microwave energy is transmitted to heat the inside of the food product.
Many types of food products typically are cooked in generally bowl-shaped containers, which generally have at least slightly flattened bottoms and which generally appear circular in a top plan view. Some of these food products such as fruit pies and pot pies include a frozen pie dough shell containing one or more suitable fillings. FIG. 1 shows one type of microwave container, a bowl 10, that is used to cook a food product having a frozen pie dough shell and one or more fillings. The bowl 10 is formed from a laminate made from a layer of microwave transparent material 12, typically a polymeric sheet, on which a thin layer of electroconductive material 14 such as aluminum has been formed, typically by sputter deposition, and which has been bonded to a microwave transparent supporting substrate 16 such as a paper sheet. The thin aluminum layer 14 is sputter-deposited on the polymeric sheet to form a plain susceptor that abuts the bottom, heel, side walls, and crust of the pie dough shell when the food product (not shown) is placed in the bowl 10.
Unfortunately, the bowl 10 does not perform well in some microwave ovens for some types of food products. For example, many food products having a frozen pie dough shell container do not cook properly in the bowl 10. When such food products are exposed to microwave energy for a sufficient time to brown the pie dough shell, some part of the filling may not be sufficiently heated due to the excess reflection of microwave power by the susceptor. On the other hand, if the food product within the bowl 10 is exposed to microwave energy for an extended period of time to ensure that the filling is sufficiently cooked throughout, portions of the filling may overheat and parts of the pie dough shell may overcook or burn.
It is desirable to develop a microwave container for food products generally, and particularly a microwave bowl for a pie dough shell food product, that adequately and relatively uniformly cooks the filling in a pie dough shell while suitably browning the pie dough shell.
Advantageously, an aspect of the patterned susceptor of the present invention has improved uniformity and adequacy of cooking relative to the plain susceptor of the prior art when used to cook certain food products, especially food products having a frozen pie dough shell containing a filling.
Advantageously, an aspect of the patterned susceptor of the present invention, when used in a container, has a reduced tendency toward de-lamination in the area between the bottom and sidewall of the container.
These and other advantages are realized separately or in combination in various embodiments of the present invention. One embodiment of the present invention is a microwave heating surface comprising a plurality of non-overlapping closed curvilinear heating regions distributed generally throughout the heating surface, at least a first one of the closed curvilinear heating regions comprising a first plurality of discrete microwave absorptive features that are spaced-apart for enhancing microwave transmission and reducing microwave reflectance of the heating surface under load relative to a plain susceptor.
Another embodiment of the present invention is a microwave heating surface comprising a plurality of discrete microwave absorptive features distributed generally throughout the microwave heating surface in a plurality of non-overlapping closed curvilinear heating regions and spaced-apart for enhancing microwave transmission and reducing microwave reflectance of the heating surface under load relative to a plain susceptor.
Another embodiment of the present invention is a microwave susceptor structure comprising a first layer of microwave transparent material and a second layer of patterned microwave interactive material. The patterned microwave interactive material comprises a plurality of arrangements of microwave interactive features, the arrangements comprising repeating patterns of some of the microwave interactive features disposed generally along respective close plane curves that are generally symmetrical about at least two orthogonal axes.
Another embodiment of the present invention is a microwave susceptor structure comprising a first layer of microwave transparent material and a second layer of patterned microwave interactive material. The second layer of patterned microwave interactive material comprises a first arrangement of substantially identical first microwave interactive features along a circle of a first radius; a second arrangement of substantially identical second microwave interactive features along a circle of a second radius greater than the first radius, the second arrangement being concentric with the first arrangement; a third arrangement of substantially identical third microwave interactive features along a circle of a third radius greater than the second radius, the third arrangement being concentric with the second arrangement; and a fourth arrangement of substantially identical fourth microwave interactive features along a circle of a fourth radius greater than the third radius, the fourth arrangement being concentric with the third arrangement.
Another embodiment of the present invention is a microwave susceptor structure comprising a first layer of microwave transparent material and a second layer of patterned microwave interactive material. The second layer of patterned microwave interactive material comprises a first arrangement of substantially identical first microwave interactive features along a circle of a first radius; a second arrangement of substantially identical second microwave interactive features along a circle of a second radius greater than the first radius, the second arrangement being concentric with the first arrangement; a third arrangement of substantially identical microwave transparent features along a circle of a third radius greater than the second radius, the third arrangement being concentric with the second arrangement; and a fourth arrangement of a microwave interactive strip along a circle of a fourth radius greater than the third radius, the fourth arrangement being concentric with the third arrangement.
Another embodiment of the present invention is a microwave susceptor blank comprising a first layer of microwave transparent material, a second layer of patterned microwave interactive material, and a third layer of microwave transparent material. The second layer is disposed between the first and third layers. The patterned microwave interactive material comprises a bottom heating region, a fold region bounding the bottom heating region, and a sidewall region bounding the fold region. The fold region comprises a plurality of curvilinear microwave transparent features disposed generally through out the fold region in a generally repeating pattern for relieving thermal stress in the fold region during heating of the susceptor.
Another embodiment of the present invention is a microwave susceptor blank comprising a first layer of microwave transparent material; a second layer of patterned microwave absorptive material formed on the first layer and comprising a bottom heating region, a fold region bounding the bottom heating region, and a sidewall region bounding the fold region; and a third layer of microwave transparent supportive material; the first and third layers being laminated with the second layer disposed therebetween. The bottom heating region comprises a plurality of non-overlapping closed curvilinear heating regions distributed generally throughout the bottom heating region, at least a first one of the closed curvilinear heating regions comprising a first plurality of discrete spaced-apart microwave absorptive features for enhancing microwave transmission and reducing microwave reflectance of the bottom heating region under load relative to a plain susceptor. The fold region comprises a generally continuous microwave absorptive feature having a plurality of curvilinear microwave transparent features disposed therein in a generally repeating pattern for relieving thermal stress in the fold region upon exposure thereof to microwave energy. The sidewall region comprises a generally continuous microwave absorptive feature.
Another embodiment of the present invention is a microwave container comprising a bottom heating region, a fold region, and a sidewall region disposed on a microwave transparent supporting substrate. The bottom heating region comprises a plurality of non-overlapping closed curvilinear heating regions distributed generally throughout the bottom heating region and disposed on a microwave transparent supporting substrate, at least a first one of the closed curvilinear heating regions comprising a first plurality of discrete microwave absorptive features that are spaced-apart for enhancing microwave transmission and reducing microwave reflectance of the bottom heating region under load relative to a plain susceptor. The fold region is disposed about the bottom region and comprises a generally continuous microwave absorptive feature having a plurality of curvilinear microwave transparent features disposed therein in a generally repeating pattern for relieving thermal stress in the fold region upon exposure to microwave energy. The sidewall region is disposed about the fold region and comprises a generally continuous microwave absorptive feature.
Another embodiment of the present invention is a microwave container comprising a bottom region, a fold region disposed about the bottom region, and a sidewall region disposed about the fold region. The bottom region, the fold region, and the sidewall region are formed from a laminated material comprising a first layer of microwave transparent material, a second layer of patterned microwave interactive material, and a third layer of microwave transparent material, the second layer being disposed between the first and third layers. The patterned microwave interactive material in the bottom region comprises a plurality of arrangements of microwave interactive features, the arrangements comprising repeating patterns of some of the microwave interactive features disposed generally along respective close plane curves that are generally symmetrical about at least two orthogonal axis. The patterned microwave interactive material in the fold region comprises a plurality of curvilinear microwave transparent features disposed generally through out the fold region in a generally repeating pattern for relieving thermal stress in the fold region during microwave heating. The patterned microwave interactive material in the sidewall region comprising a microwave interactive strip disposed generally throughout the sidewall region.